Pediatr Radiol (1992) 22:467-468
Pediatric Radiology 9 Springer-Verlag 1992
Inflammatory pseudotumor of the lung manifesting as a posterior mediastinal mass I. Kim 1, W. S. Kim 1, K. M. Yeon l, J. G. Chi 2 Department of Diagnostic Radiology, Seoul National University Children's Hospital, Seoul, 110-744, Korea 2Department of Pathology, Seoul National University Children's Hospital, Seoul, 110-744, Korea Received: 21 April 1992; accepted: 18 June 1992
Abstract. A case of inflammatory pseud o t u m o r of the lung in a 6-year-old b o y is presented. The respiratory illness presented as a m y c o p l a s m a p n e u m o n i a and there h a d b e e n a similar episode of mycoplasma p n e u m o n i a one and a half years previously. C o m p u t e d tomography revealed a large, calcified right posterior mediastinal mass and exploratory t h o r a c o t o m y revealed a large posterior mediastinal mass that had an endobronchial c o m p o n e n t and grew exophytically from the lung. The present case suggests that inflammatory pseudot u m o r of the lung can manifest as a mediastinal mass and could be associated with m y c o p l a s m a p n e u m o n i a infection. I n f l a m m a t o r y p s e u d o t u m o r is a nonneoplastic, reactive p u l m o n a r y mass lesion that resembles t u m o r but shows little or no growth [1]. It is the most common cause of primary tumor-like, benign lesion of the lung in children [2], although it is often forgotten in the differential diagnosis. The radiological manifestations are quite diverse and the origin and histogenesis of this lesion is not clear. This r e p o r t describes the unusual CT finding of a case of inflammatory p s e u d o t u m o r manifest as a posterior mediastinal mass and discusses the etiologic concern about th m y c o p l a s m a p n e u m o n i a infection.
Case report A six-year-old boy was admitted with high fever up to 40 ~ and cough. He was treated as an upper respiratory infection, but the symptoms persisted. One and a half years preCorrespondence to: Dr. I. Kim, Department of Diagnostic Radiology, Seoul National University Children's Hospital, 28 Yongon-Dong Chongno-Gu, Seoul, 110-774, Korea
viously, he had been admitted for 5 days under the impression of mycoplasma pneumonia, showing dense consolidation in the right lower lung without pleural effusion or hilar adenopathy on plain radiography. At that time, cold agglutinin against mycoplasma was 1:32 and antinlycoplasmal antibody was positive at 1:16 and 1:80 after 13 days. Hewas managed with sodium penicillin and followup antimycoplasmal antibody converted to negative. On this admission, the white blood cell count was 25 400 (polymorphs 84.9 %, lymphocytes 9.6%) and antimycoplasmal antibody was positive at 1:40. No infectious agent was identified despite several sputum smear and culture studies. The chest radiograph showed mass like consolidation occupying the right lower lung field and computed tomography showed a 4 x 7 x 7 cm, well-delineated soft tissue mass containing dense irregular calcifications (Figs. 1, 2). The mass lesion was attached to the posteromedial aspect of the right middle lobe and displaced the inferior vena cava and right atrium anteriorly. The fight middle and lower lobes were collapsed and a small amount of pleural effusion was present. Aspiration cytology showed numerous neutrophils and fibroblast-like spindle ceils suggesting an inflammatory lesion. Exploratory thoracotomy revealed a large solitary mass located in the lung parenchyma and protruding into the mediastinum. The middle and lower lobes were consolidated and collapsed. The mass, together with the right middle and lower lobes, was resected. Part of the mass was protruding into the right middle lobe bronchial lumen (Fig. 3). Postoperative diagnosis was malignant teratoma. On gross examination, the mass was located in the right middle lobe and approximately three quarters of the mass grew outside the lung. The mediastinal aspect of the mass was covered with visceral pleura. On sectioning, the mass felt gritty and connected to the right middle 1obar bronchus with a polypoid endobronchial lesion occluding onethird of the lumen. The cut surface was greytan and slightly trabeculated with multifocal calcifications. Microscopically, the mass was composed of interlacing bundles of bland-
looking plasma cells,lymphocytes, and histiocytes. The plasma cells were scattered individually and collected around vessels and entrapped alveoli and they showed occasional binucleation and Russell bodies. Ultrastructurally, the lesion was composed of elongated and plump fibroblasts, myofibroblasts and infiltrated plasma cells, lymphocytes and histiocytes in a background of collagen. The adjacent lung parenchyma showed features of bronchiolitis obliterans. The pathologic diagnosis was inflammatory pseudotumor of the lung. The postoperative course was uneventful and the patient remains in good condition.
Discussion I n f l a m m a t o r y p s e u d o t u m o r of the lung is considered to be a non-neoplasticmass lesion of unknown cause and pathogenesis, which is c o m p o s e d of a variety of inf l a m m a t o r y and mesenchymal cells, including plasma cells, histiocytes which are often xanthomatous, mast cells, histiocytes which are often xanthomatous, mast cells, lymphocytes and spindles h a p e d mesenchymal cells [1]. A numb e r of synonyms, based on p r e d o m i n a n t cell types, have b e e n used to describe the lesion, adding to the confusion, but recently, however, the t e r m "inflammatory p s e u d o t u m o r of the lung" seems to have b e c o m e widely accepted. The pathogenesis has been attributed by B ahadori and Liebow to a reactive inflammatory process via a disturbed immunologic reaction [3]. It is a benign lung mass, most commonly occurring in the lung p a r e n c h y m a and less c o m m o n l y in the trachea and main bronchi. It is r e p o r t e d that one third of the lesions occur b e l o w t h e age of twenty years and 25 % occur below ten years. Radiologically it usually appears as a solitary, circumscribed, r o u n d or oval mass varying in size from 0.5 to 36 cm in diameter. Less commonly the lesions are ill-defined, resembling areas
468
Fig. 1. Chest X-ray reveals a triangular haziness in the right lower lung Fig.2. Chest CT reveals a round posterior mediastinal mass containing chunky calcifications attached to the midial aspects of the right middle lobe Fig. 3. Resected specimen showing the medial aspect of the right middle lobe shows exophytically projecting mass with endobronchial component (arrows)
of pneumonia or atelectasis. Occasionally, endobronchial lesions may cause a postobstructive pneumonia or atelectasis. It may behave in a more aggressive fashion to encase the bronchi and extend into the mediastinal structures, chest wall, or diaphragm [4, 5]. Calcification within the mass can be seen up to 5 % of cases, more frequently in childhood [6]. The present case seems to be the aggressive type, involving the bronchus and extending into the mediastinum. Various theories about the cause and pathogenesis of the inflammatory pseudotumor have been suggested such as metabolic disturbance, response to an
immunologic process, association with pulmonary infection, and a variant of postinflammatory repair process, but none has been proved. Janigan and Marrie have reported a case associated with Coxiella burnetii pneumonia [7]. We suspect that the present case might be associated with Mycoplasma pneumonia although we failed to culture the organism. In summary, we present a case of inflammatory pseudotumor of the lung in a child that might be associated with mycoplasma pneumonia infection and had an indolent course despite of a large mass which involved the right lung with
endobronchial and mediastinal involvement.
References 1. Berardi RS, Lee SS, Chen HE Stines GJ (1983) Inflammatory pseudotumors of the lung. Surg Gynecol Obstet 156:89 2. Hartmann GE, Shochat SJ (1983) Primary pulmonary neoplasms of childhood: a review. Ann Thorac Surg 36:108 3. Bahadori M, Liebow A (1973) Plasma cell granuloma of the lung. Cancer 31:191 4. Shapiro ME Elon Gale M, Carter BL (1987) Variable CT appearance of plasma cell granuloma of the lung. J Assist Comput Tomogr 11:49 5. Laufer L, Cohen Z, Mares AJ, Maor E, Hirsch M (1990) Pulmonary plasma cell granuloma. Pediatr Radio120:289 6. Kaufmann RA (1988) Calcified postinflammatory pseudotumor of the lung: CT features. J Comput Assist Tomogr 12:653 7. Janigan DT, Marrie TJ (1983) An inflammatory pseudotumor of the lungin Q fever pneumonia. N Engl J Med 308:86
Pediatric Radiology 9 Springer-Verlag 1992
Inflammatory pseudotumor of the lung manifesting as a posterior mediastinal mass I. Kim 1, W. S. Kim 1, K. M. Yeon l, J. G. Chi 2 Department of Diagnostic Radiology, Seoul National University Children's Hospital, Seoul, 110-744, Korea 2Department of Pathology, Seoul National University Children's Hospital, Seoul, 110-744, Korea Received: 21 April 1992; accepted: 18 June 1992
Abstract. A case of inflammatory pseud o t u m o r of the lung in a 6-year-old b o y is presented. The respiratory illness presented as a m y c o p l a s m a p n e u m o n i a and there h a d b e e n a similar episode of mycoplasma p n e u m o n i a one and a half years previously. C o m p u t e d tomography revealed a large, calcified right posterior mediastinal mass and exploratory t h o r a c o t o m y revealed a large posterior mediastinal mass that had an endobronchial c o m p o n e n t and grew exophytically from the lung. The present case suggests that inflammatory pseudot u m o r of the lung can manifest as a mediastinal mass and could be associated with m y c o p l a s m a p n e u m o n i a infection. I n f l a m m a t o r y p s e u d o t u m o r is a nonneoplastic, reactive p u l m o n a r y mass lesion that resembles t u m o r but shows little or no growth [1]. It is the most common cause of primary tumor-like, benign lesion of the lung in children [2], although it is often forgotten in the differential diagnosis. The radiological manifestations are quite diverse and the origin and histogenesis of this lesion is not clear. This r e p o r t describes the unusual CT finding of a case of inflammatory p s e u d o t u m o r manifest as a posterior mediastinal mass and discusses the etiologic concern about th m y c o p l a s m a p n e u m o n i a infection.
Case report A six-year-old boy was admitted with high fever up to 40 ~ and cough. He was treated as an upper respiratory infection, but the symptoms persisted. One and a half years preCorrespondence to: Dr. I. Kim, Department of Diagnostic Radiology, Seoul National University Children's Hospital, 28 Yongon-Dong Chongno-Gu, Seoul, 110-774, Korea
viously, he had been admitted for 5 days under the impression of mycoplasma pneumonia, showing dense consolidation in the right lower lung without pleural effusion or hilar adenopathy on plain radiography. At that time, cold agglutinin against mycoplasma was 1:32 and antinlycoplasmal antibody was positive at 1:16 and 1:80 after 13 days. Hewas managed with sodium penicillin and followup antimycoplasmal antibody converted to negative. On this admission, the white blood cell count was 25 400 (polymorphs 84.9 %, lymphocytes 9.6%) and antimycoplasmal antibody was positive at 1:40. No infectious agent was identified despite several sputum smear and culture studies. The chest radiograph showed mass like consolidation occupying the right lower lung field and computed tomography showed a 4 x 7 x 7 cm, well-delineated soft tissue mass containing dense irregular calcifications (Figs. 1, 2). The mass lesion was attached to the posteromedial aspect of the right middle lobe and displaced the inferior vena cava and right atrium anteriorly. The fight middle and lower lobes were collapsed and a small amount of pleural effusion was present. Aspiration cytology showed numerous neutrophils and fibroblast-like spindle ceils suggesting an inflammatory lesion. Exploratory thoracotomy revealed a large solitary mass located in the lung parenchyma and protruding into the mediastinum. The middle and lower lobes were consolidated and collapsed. The mass, together with the right middle and lower lobes, was resected. Part of the mass was protruding into the right middle lobe bronchial lumen (Fig. 3). Postoperative diagnosis was malignant teratoma. On gross examination, the mass was located in the right middle lobe and approximately three quarters of the mass grew outside the lung. The mediastinal aspect of the mass was covered with visceral pleura. On sectioning, the mass felt gritty and connected to the right middle 1obar bronchus with a polypoid endobronchial lesion occluding onethird of the lumen. The cut surface was greytan and slightly trabeculated with multifocal calcifications. Microscopically, the mass was composed of interlacing bundles of bland-
looking plasma cells,lymphocytes, and histiocytes. The plasma cells were scattered individually and collected around vessels and entrapped alveoli and they showed occasional binucleation and Russell bodies. Ultrastructurally, the lesion was composed of elongated and plump fibroblasts, myofibroblasts and infiltrated plasma cells, lymphocytes and histiocytes in a background of collagen. The adjacent lung parenchyma showed features of bronchiolitis obliterans. The pathologic diagnosis was inflammatory pseudotumor of the lung. The postoperative course was uneventful and the patient remains in good condition.
Discussion I n f l a m m a t o r y p s e u d o t u m o r of the lung is considered to be a non-neoplasticmass lesion of unknown cause and pathogenesis, which is c o m p o s e d of a variety of inf l a m m a t o r y and mesenchymal cells, including plasma cells, histiocytes which are often xanthomatous, mast cells, histiocytes which are often xanthomatous, mast cells, lymphocytes and spindles h a p e d mesenchymal cells [1]. A numb e r of synonyms, based on p r e d o m i n a n t cell types, have b e e n used to describe the lesion, adding to the confusion, but recently, however, the t e r m "inflammatory p s e u d o t u m o r of the lung" seems to have b e c o m e widely accepted. The pathogenesis has been attributed by B ahadori and Liebow to a reactive inflammatory process via a disturbed immunologic reaction [3]. It is a benign lung mass, most commonly occurring in the lung p a r e n c h y m a and less c o m m o n l y in the trachea and main bronchi. It is r e p o r t e d that one third of the lesions occur b e l o w t h e age of twenty years and 25 % occur below ten years. Radiologically it usually appears as a solitary, circumscribed, r o u n d or oval mass varying in size from 0.5 to 36 cm in diameter. Less commonly the lesions are ill-defined, resembling areas
468
Fig. 1. Chest X-ray reveals a triangular haziness in the right lower lung Fig.2. Chest CT reveals a round posterior mediastinal mass containing chunky calcifications attached to the midial aspects of the right middle lobe Fig. 3. Resected specimen showing the medial aspect of the right middle lobe shows exophytically projecting mass with endobronchial component (arrows)
of pneumonia or atelectasis. Occasionally, endobronchial lesions may cause a postobstructive pneumonia or atelectasis. It may behave in a more aggressive fashion to encase the bronchi and extend into the mediastinal structures, chest wall, or diaphragm [4, 5]. Calcification within the mass can be seen up to 5 % of cases, more frequently in childhood [6]. The present case seems to be the aggressive type, involving the bronchus and extending into the mediastinum. Various theories about the cause and pathogenesis of the inflammatory pseudotumor have been suggested such as metabolic disturbance, response to an
immunologic process, association with pulmonary infection, and a variant of postinflammatory repair process, but none has been proved. Janigan and Marrie have reported a case associated with Coxiella burnetii pneumonia [7]. We suspect that the present case might be associated with Mycoplasma pneumonia although we failed to culture the organism. In summary, we present a case of inflammatory pseudotumor of the lung in a child that might be associated with mycoplasma pneumonia infection and had an indolent course despite of a large mass which involved the right lung with
endobronchial and mediastinal involvement.
References 1. Berardi RS, Lee SS, Chen HE Stines GJ (1983) Inflammatory pseudotumors of the lung. Surg Gynecol Obstet 156:89 2. Hartmann GE, Shochat SJ (1983) Primary pulmonary neoplasms of childhood: a review. Ann Thorac Surg 36:108 3. Bahadori M, Liebow A (1973) Plasma cell granuloma of the lung. Cancer 31:191 4. Shapiro ME Elon Gale M, Carter BL (1987) Variable CT appearance of plasma cell granuloma of the lung. J Assist Comput Tomogr 11:49 5. Laufer L, Cohen Z, Mares AJ, Maor E, Hirsch M (1990) Pulmonary plasma cell granuloma. Pediatr Radio120:289 6. Kaufmann RA (1988) Calcified postinflammatory pseudotumor of the lung: CT features. J Comput Assist Tomogr 12:653 7. Janigan DT, Marrie TJ (1983) An inflammatory pseudotumor of the lungin Q fever pneumonia. N Engl J Med 308:86
